The present invention generally relates to techniques for operating a disk drive apparatus. More particularly, the present invention provides techniques for creating a vertical offset between hinge fingers in a disk drive suspension assembly in order to reduce track mis-registration error.
A hard disc drive (HDD) unit generally uses a spinning storage medium (e.g., a disk or platter) to store data. A read-write head is positioned in close proximity to the spinning storage medium by an HSA (Head Stack Assembly). Mounted on the HSA, a suspension assembly commonly includes a base plate, a load beam, and a flexure trace gimbal to which a slider is mounted. Alternatively the read-write head may be positioned by an integrated arm mounting assembly (known in the art as “Unimount”) including a mount plate adapted to a pivot bearing assembly at the proximal end and a load beam, flexure trace gimbal, and slider at the distal end. The slider supports the read-write head element. The load beam is generally composed of an actuator mounting region, a spring region, and a rigid region. The spring region gives the suspension a spring force or preload to counteract the aerodynamic lift force created by the spinning storage medium during reading or writing. A gimbal is mounted at the distal end of the load beam and supports the slider allowing the head to have pitch and roll movement in order to follow the irregularities of the disk surface.
Demand generally requires increased HDD storage capacity, which generally compels higher data track densities for the storage medium. Furthermore, the demand for faster rates of data seeking and accessing also leads to higher rotational speeds. A significant obstacle associated with increasing rotational speeds and storage capacity is often head positioning accuracy as the head flies above the spinning storage medium.
A significant obstacle to head positioning accuracy is disk flutter. Disk flutter is an aero-elastic instability induced by the coupling of the spinning storage medium and the air surrounding the media resulting in disk vibration modes. These flow induced vibrations can physically cause an off-track misalignment of the head to the desired track resulting in failure to access or write data on the track center. Problems associated with disk flutter become more intolerable with higher track densities and disk rotation speeds.
The desirability of introducing a vertical offset in the hinges in a head suspension is described in U.S. patent application Ser. Nos. 11/119,363 and 11/119,364, both of which were filed on Apr. 29, 2005, both of which are assigned to the assignee of the present application, and both of which are herein incorporated by reference. The present invention provides structures and techniques for producing head suspension assemblies which incorporate the desired vertical offset.